1. Field of the Invention
The present invention is directed to capturing objects beyond an operative site in any of a variety of medical procedures employed to treat any number of medical conditions in human and/or animal patients.
2. Description of the Prior Art
In many medical procedures, objects are dislodged or otherwise freed by the surgeon during the surgical procedure, and it is useful and/or necessary to capture the dislodged and/or otherwise freed object.
Although minimally invasive interventional medical therapies in general, and minimally invasive endovascular therapy in particular, are medical procedures where objects may be dislodged or otherwise freed during the procedure, each has enjoyed unprecedented expansion to treat patients because of the numerous medical benefits associated with not having to enter the body through more invasive surgical techniques. These benefits include, but are not limited to, less trauma and/or scarring for patients, less time to heal, less risk of infection and decreased hospital stays, to name but a few.
More particularly, minimally invasive endovascular therapy is often used to treat diseased vessels, e.g., arteries and veins. With such therapy, small instruments are inserted into the vessels through a puncture or access opening made in one of the vessels at an entry site and are advanced through the circulatory system to an operative site where the vessel has become diseased, and the instruments are used to repair the diseased or operative site.
Typically, the goal of such therapy is to dilate full or partial blockages of the diseased vessel. Such blockages may have developed over time or may have developed quickly, as for example, in response to an injury. One common source of such blockage is thromboemboli which has formed in the vessel. Thrombus is an aggregation of platelets, fibrin, clotting factors and cellular components of blood that spontaneously form and attach on the interior wall of a vein or artery, and thromboemboli are emboli of thrombus which operate to partially or completely occlude the interior or lumen of the blood or other vessel.
Techniques to open and/or maintain the dilation of the partially or completely occluded lumen of blood or other vessels include positioning a balloon across an obstruction or partially occluded section of the vessel, inflating the balloon to compress the build up (balloon angioplasty) and/or temporarily or permanently inserting a tube-like support within the vessels to keep the vessel open (stenting).
Minimally invasive endovascular therapy has the significant advantage that it is less invasive than traditional surgical techniques and causes less trauma to the patient. However, this therapy is complicated by the fact that it can undesirably dislodge or free particles/objects during the procedure as discussed above, and in that the tools or instruments and workspace, e.g., the interior of the vessels of the body, are in some cases extremely small and close, and reaching the operative site with the tools is very difficult in some instances due to the considerable branching of the circulatory system that may occur between the entry site into the blood vessel and the operative site. This therapy is further complicated by the fact that the entry site is often far from the operative site, as for example, where the entry site is in the thigh at the femoral artery and the operative site is located in the neck at the carotid artery. Even when the surgeon's instruments have been properly advanced to the operative site, manipulating the tools to perform their respective functions at the operative site is often difficult for the surgeon due to many factors including the close quarters at the operative site and the distance between the entry site and the operative site.
One method and apparatus commonly used by surgeons to ensure the tools reach the operative site is to first thread a simple guide wire to or beyond the operative site. Thereafter, various tools are threaded over the guide wire by the surgeon to reach the operative site. It is an important aspect of such guide wires that they must be easy to manipulate through the vessels, including in certain cases, through lesions or areas of blockage in the vessel by the surgeon. In addition to exhibiting sufficient resiliency so as to be pushable in the vessel, the guide wire must exhibit sufficient flexibility and maneuverability to enable the surgeon to traverse the many twists and turns of the circulatory (or other) system to reach the operative site.
An aspect of the ability for a surgeon to manipulate the guide wire through the circulatory or other system is the guide wire's “torquability”. As defined herein, the term “torquability” means that as the surgeon rotates the proximal region of the guide wire that extends outside of the patient's body during the advancement of the guide wire through the patient's blood or other vessels to the operative site, the amount of rotation at the proximal region of the guide wire is transmitted to the distal end of the guide wire being inserted and advanced through the patient's blood or other vessels to the operative site. A lack of correlation between rotation at the proximal region of the guide wire and rotation at the distal end of the guide wire is referred to as reduced torquability and is undesirable. A high degree of correlation is referred to as a high degree of torquability and is desirable. As may be appreciated, it is most desirable for the guide wire to have an exact correlation or high torquability between the rotation applied proximally at the proximal region of the guide wire and the rotation developed distally in the guide wire, so that the surgeon can carefully control and direct the medical guide wire. With known devices, there is considerable difference between the amount of rotation applied at the proximal region of the guide wire and the amount of rotation developed at the distal end of the guide wire, making it very difficult for surgeons to maneuver the distal end of the guide wire.
Even where the guide wire exhibits the desired torquability characteristics, and the tools have been properly threaded to the operative site and have been properly manipulated to perform their respective functions at the operative site, there remains the problem noted above, namely, that the process of dilating the occlusion and/or inserting the stent may dislodge or free small particles or objects, also known, among other things, as clots, fragments, plaque, emboli, thromboemboli, etc. More particularly, with respect to endovascular therapy, the term “embolic event” has come to be used to describe complications where thrombus or plaque is shed inadvertently from a lesion to migrate to smaller vessels beyond the operative site to create a full or partial occlusion of the lumen of the vessel or vessels. This is most undesirable and can lead to many complications. Complications depend upon the site in the body where such emboli lodge downstream of the operative site, but may include stroke, myocardial infarction, kidney failure, limb loss or even death. With increasing vigor, surgeons have expressed the need to reduce the likelihood of such complications so that protection against embolic events will become a standard component of endovascular therapy.
Devices have been made in the art to capture objects, including emboli, downstream of an operative site in medical procedures, including endovascular therapy. Such devices generally employ a capture device, such as a bag or filter, which has a collapsed state and an expanded or deployed state. Typically, the capture device is maintained in its collapsed state within sheathing and is inserted into the blood or other vessel and is threaded beyond the operative site. It is then ejected from the sheathing whereupon it expands to its deployed state to capture the objects dislodged or otherwise freed during the medical procedure.
One device for removing clot or filtering particles from blood is described in U.S. Pat. No. 4,723,549 to Wholey et al., which discloses a device for dilating occluded blood vessels. This device includes a collapsible filter device positioned between a dilating balloon and the distal end of the catheter. The filter comprises a plurality of resilient ribs secured to the catheter that extend axially toward the dilating balloon. Filter material is secured to the ribs. The filter deploys as a balloon is inflated to form a cup-shaped trap. An important limitation of the Wholey et al. device appears to be that the filter does not seal around the interior vessel wall. Thus, particles sought to be trapped in the filter can instead undesirably pass between the filter and the vessel wall and flow downstream in the circulatory system to produce a blockage. Another limitation is that the device also presents a large profile during positioning. Yet another limitation appears to be that the device is difficult to construct.
U.S. Pat. No. 4,873,978 to Ginsburg discloses a vascular catheter that includes a strainer device at its distal end. The device is inserted into a vessel downstream from the treatment site and advanced to a proximal downstream location. The filter is contained in a sheath when closed. When pushed from the sheath, the filter deploys such that its mouth spans the lumen of the vessel. Deployment is by expansion of resilient tines to which the strainer material is attached. Again, however, it appears that the filter does not seal around the interior vessel wall, thus undesirably allowing particles to bypass the filter by passing between the filter and the vessel wall. The position of the mouth relative to the sheath is also clinically limiting for the Ginsburg device.
U.S. Pat. No. 5,695,519 to Summers et al. discloses a removable intravascular filter on a hollow guide wire for entrapping and retaining emboli. The filter is deployable by manipulation of an actuating wire that extends from the filter into and through the hollow tube and out the proximal end. One limitation with the Summers et al. device appears to be that its filter material is not fully constrained. Therefore, during positioning within a vessel, as the device is positioned through and past a clot, the filter material can snag clot material undesirably creating freely floating emboli. It is unclear if the actuating wire can close the filter, and it appears in any event that it will exert a pull force on the rim of the filter that could tear the wire from the rim. Another limitation appears to be that the device application is limited by the diameter of the tube needed to contain the actuating wire.
U.S. Pat. No. 5,814,064 to Daniel et al. discloses an emboli capture device on a guide wire. The filter material is coupled to a distal portion of the guide wire and is expanded across the lumen of a vessel by a fluid activated expandable member in communication with a lumen running the length of the guide wire. One limitation of the device appears to be that during positioning, as the device is passed through and beyond the clot, filter material may interact with the clot so as to undesirably dislodge material and produce emboli. It is further believed that the device may also be difficult to manufacture. Another limitation is that it is difficult to determine the amount of fluid needed to expand the member. A lack of control can rupture and tear the smaller vessels. Thus, the Daniel et al. device would appear to be more compatible with use in the larger vessels only.
PCT Publication No. WO 98/33443 discloses a removable vascular filter wherein the filter material is fixed to cables or spines mounted to a central guide wire. A movable core or fibers inside the guide wire can be utilized to transition the cables or spines from approximately parallel the guide wire to approximately perpendicular the guide wire. A limitation of this device appears to be that the filter does not seal around the interior vessel wall. Thus, particles, e.g., emboli-forming materials, can undesirably bypass the filter by passing between the filter and the vessel wall. Another limitation appears to be that this umbrella-type device is shallow when deployed so that, as it is being closed for removal, the particles it was able to ensnare could escape. Yet another limitation is that the frame is such that the introduction profile presents a risk of generating emboli as the device is passed through and beyond the clot, occlusion or stenosis.
U.S. Pat. No. 5,769,816 to Barbut et al. discloses a device for filtering blood within a blood vessel. The device is delivered through a cannula and consists generally of a cone-shaped mesh with apex attached to a central support and open edge attached to an inflation seal that can be deflated or inflated. The seal is deflated during delivery and when delivery is complete, it is inflated to seal the filter around the lumen of the vessel. Limitations of this device include that it is complex to manufacture. Inflation and deflation of the seal adds additional operative steps thus prolonging the operation-and introducing the issue again of control, e.g., of how much to inflate to obtain a seal without causing damage to the vessel or other material. While the device may be suitable for large vessels, such as the aorta, is would be most difficult to scale for smaller vessels, such as the carotid or the coronary arteries.
U.S. Pat. No. 5,549,626 to Miller et al. discloses a coaxial filter device for removing particles from arteries and veins consisting of an outer catheter that can be inserted into a blood vessel and an inner catheter with a filter at its distal end. The filter is a radially expandable receptacle made of an elastic mesh structure of spring wires or plastic monofilaments. When pushed from the distal end of the catheter, the filter deploys across the vessel lumen. A syringe attached to the proximal end of the inner catheter aspirates particles entrapped in the filter. One limitation of this device appears to be that it is possible that some particles will remain in the filter after aspiration such that, when the filter is retracted into the outer catheter, particles not aspirated are undesirably released into the circulatory system.
U.S. Pat. No. 6,027,520 to Tsugita et al. discloses a method and system for embolic protection consisting of a filter on a guide wire coupled with a separate stent catheter deployed over the guide wire. One limitation of the Tsugita et al. device is that the many filter designs summarized in the patent generally lack a controllable, conformable circumferential support in the mouth of the filters to ensure they seal around the inside of a blood vessel. Without such a seal, it is again possible for particulate material to evade the filter by undesirably passing between the filter and the vessel wall, whereupon the particulate material may flow downstream of the operative or other site to produce full or partial blockage of the vessels. Many of the Tsugita et al. filter expansion devices utilize multiple struts to open the filter. These are not desirable as they increase the profile of the device when crossing a lesion, in turn, reducing the range of clinical cases on which they can be used. Further, such designs add stiffness to the region of the undeployed filter which can impede the surgeon's ability to direct the guide wire through the complex twists and turns of the circulatory system to the operative site, e.g., making it difficult to direct the device into a branching vessel. Also, the Tsugita et al. design is burdened by its use of a long deployment sheath to hold the filter in a collapsed state and direct it to the operative site. The Tsugita et al. sheath extends from a hemostatic seal at the site of entry into the blood or other vessel to the operative site (see column 7, lines 56–58. and also column 8, lines 19–30 of the Tsugita et al. patent). This long sheath, necessary in the Tsugita et al. design, significantly impairs the ability to direct the guide wire through the circulatory system to the operative site. Not only is such a sheath an impairment to directing the guide wire around the twists and turns of the circulatory system, but such a sheath also “loads” the guide wire, which operates to significantly reduce the Tsugita et al. system's torquability, greatly reducing the ability of the surgeon to control the guide wire and guide it through tight lesions.
At column 7, lines 28–32, Tsugita et al. states that its stent may comprise a tube, sheet, wire, mesh or spring, and goes on to state that such a stent can cover the plaque and substantially permanently trap it between the stent and the wall of the vessel. (see column 9, lines 55–58 of the Tsugita et al. patent) However, this is not accurate, and depending upon the type of stent, not only will it not trap such plaque, but plaque can reform through the interstices of the mesh whereupon the vessel can again become fully or partially occluded.
These shortcomings are present whether the stent is mechanically expandable or self expanding. Relative to mechanically expandable stents, they are delivered with a stent catheter. See U.S. Pat. Nos. 5,507,768; 5,158,548 and 5,242,399 to Lau et al. incorporated herein by reference. The catheter has an inflatable balloon at or near the distal end on which the stent is mounted. An inflation lumen runs the length of the catheter to the balloon. Generally, the stent is a tubular mesh sleeve. See U.S. Pat. No. 4,733,665 to Palmaz incorporated herein by reference. A self-expanding stent is typically made of Nitinol. It is compressed within a catheter until deployment. It is pushed from the catheter to deploy it. Both types of stents tend to create embolic particles. Also, both allow stenotic material to build up through the interstices of the wire mesh that could again occlude the artery.
Permanent filters for the vena cava are well-established clinical devices. These open filters capture large emboli passing from a surgical site to the lungs. U.S. Pat. No. 3,952,747 to Kimmell, Jr. et al. discloses the Kimray-Greenfield filter. It is a permanent filter typically placed in the vena cava and consists of a plurality of convergent legs in a generally conical array Each leg has a hook at its end to impale the interior wall of the vena cava. U.S. Pat. Nos. that are joined at their convergent ends to an apical hub. U.S. Pat. No. 4,425,908 to Simon; U.S. Pat. No. 4,688,553 to Metals; and U.S. Pat. No. 4,727,873 to Mobin-Uddin are also illustrative of such devices.
U.S. Pat. Nos. 5,669,933 and 5,836,968 to Simon et al. are illustrative of removable blood clot filters suitable for the venous system, specifically the vena cava.
However, the presently available capture devices all suffer from the limitation that they are not easily manipulated in the patient's body. They usually include tube-like sheathing material which extends all along the length of the guide wire used to insert the capture device into the vessel, generally extending from the entry site into the body, also known as an access port or access opening to the operative site, which sheathing operates to contain the capture device until its desired deployment in the vessel beyond the operative site. Such sheathing material operates to reduce torquability of the guide wire used to insert the capture device and operates to significantly reduce the flexibility of wire within the circulatory or other system as noted above. Removal without causing excessive movement of the deployed filter is also a problem. As the sheath is pulled from the access port during removal, the surgeon must continually reposition his hand to hold the wire used to insert the capture device, that is, as the sheath is pulled through the access port, the surgeon must release the wire and then re-grasp further down from the access port. As the surgeon's hand grasps the wire further from the access port, the more difficult it becomes to steady the guide wire as the sheath is withdrawn. As such, the capture device may move back and forth, and as it is generally at this point in its expanded state, the constant rubbing of the wall of the blood or other vessel or canal by the capturing device may irritate or injure the wall of the blood or other vessel or canal. Another complication is that several capture devices include bulky or complex deployment mechanisms, and further, when deployed, fail to fully seal around the interior of the vessel or other wall or fail to prevent unwanted release of captured particles, fragments, objects, emboli, etc., whereupon such particles, fragments, objects, emboli, etc. can undesirably escape and travel beyond the capture device.
Thus, there is a need in the art for a capture device and methods of constructing and using such device, which is easily threaded through the vessels or canals of humans and/or animals to reach an operative site, which exhibits excellent torquability, flexibility and maneuverability, which is easily removable along with its captured objects once the medical procedure has been completed without injuring or irritating the wall of the vessel or canal, and which forms a seal with the wall of the vessel or canal or otherwise prevents the undesirable escape of particles, fragments, objects, emboli, etc. beyond the capture device during surgery. There also is a need in the art for a system of associating surgical tools with such a capture device to provide protection downstream of an operative site for the capture of objects dislodged and/or freed during the medical procedure.